WASHINGTON (AP) — The Trump administration says a foreign disinformation campaign is underway aimed at spreading fear in the country amid the coronavirus pandemic, including spreading the false rumor that the nation would be locked down in quarantine, three U.S. officials said Monday.

The rumors, coupled with a cyber incident involving computer networks at the Department of Health and Human Services, prompted coordinated action Sunday evening by agencies across the government to deny that any such plans were put in place, as they tried to calm a nation already on edge because of massive disruptions to daily life.

“Text message rumors of a national #quarantine are FAKE,” tweeted the National Security Council Sunday night. “There is no national lockdown.” The NSC encouraged Americans to follow official government guidance.

It was unclear if the disinformation effort was related to administration officials' complaints in recent days that China was spreading misinformation about the U.S.

U.S. officials have been struggling to control the messaging on the virus, especially after contradictory tweets from the president himself encouraging social distancing and calling criticism by Democrats over his response “ a hoax,” and discrepancies between what scientists were articulating and what the White House was saying.

States and municipalities have banned large public gatherings, closed schools, bars and restaurants, and advised people to exercise so-called social distancing to slow the spread of the virus. The Centers for Disease Control and Prevention on Sunday issued new guidance recommending against indoor gatherings larger than 50 people for the next eight weeks, though those requirements would not apply to schools.

The nation’s top infectious disease expert, Dr. Anthony Fauci, said Sunday that Americans should aim to severely curtail leaving their homes, but he did not indicate the government would order such a move. He was specifically questioned on whether he'd like to see a “national lockdown.”

"I think Americans should be prepared that they are going to have to hunker down significantly more than we as a country are doing," said Fauci, a member of the White House task force on combating the spread of coronavirus. He heads the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.

Last week, the Pentagon accused the Chinese government of promulgating “false & absurd conspiracy theories about the origin of COVID-19 blaming U.S. service members.”

Also Monday, national security officials said there had been a cyber incident involving the computer networks of Health and Human Services, but that the networks were operating normally. They didn't detail the scope of the incident.

“HHS and federal government cybersecurity professionals are continuously monitoring and taking appropriate actions to secure our federal networks,” according to National Security Council spokesman John Ullyot.

U.S. intelligence officials have repeatedly cautioned that Russia, China, Iran and other countries are engaged in ongoing efforts to influence U.S. policy and voters in elections. They engage in covert social media campaigns using fictional personae, bots, social media postings and disinformation aimed at dividing American public opinion and sowing discord in the electorate.

The Justice Department said the Russian social media effort during the 2016 presidential election and the 2018 midterms included a social media effort aimed at spreading distrust for political candidates and causing divisions on social issues, including immigration and gun control.

A report from University of Wisconsin-Madison professor Young Mie Kim made public earlier this month found that Russia-linked social media accounts are posting about the same divisive issues — race relations, gun laws and immigration — as they did in 2016, when the Kremlin polluted American voters’ feeds with messages about the presidential election. Facebook has since removed the accounts.

And rumors about the government’s response to the spreading virus have circulated online for weeks, prompting authorities in several states to urge residents to seek out trusted sources in government and news.

On Sunday, Massachusetts Gov. Charlie Baker said he’s been asked about the rumors by “senior leaders in business, healthcare, politics.”

“I’ve had community leaders and elected officials all text me or call me and say, ‘I understand on Monday you’re basically going to order everybody to shelter in place for two weeks.' The message has been exactly the same.

“We have no plans to do that.”

He said it shows the need for residents to find trusted sources of news and information, such as legitimate news organizations or public health authorities.

“There’s so much information out there,” Baker said. “Some of which is legit, but a lot of it is wild speculation.”

Texts and posts suggesting Texas, Washington and New York states would be shutting down to prevent the spread of the coronavirus escalated with screenshots of text messages circulating online that claimed that within 48 to 72 hours Trump would place the U.S. under a two-week quarantine.

New York City officials last week debunked a claim passed around in text messages claiming the city’s Metro-North trains, connecting commuters from the suburbs to the city, would be shut down and that other train service would be limited. Washington Gov. Jay Inslee also said claims that the state would soon be under quarantine were untrue.

Joan Donovan, an expert on online misinformation at Harvard University, said the text message is an especially effective piece of misinformation because it never mentions the virus by name. That means anyone embedding it in a social media post will likely escape the platforms’ automated efforts to find and remove false claims related to the virus.

Donovan said that while she hasn’t been able to trace the message’s origin, she wouldn’t be surprised to find that foreign groups are seizing on the crisis to push misinformation that can divide or frighten Americans. “Anybody that is interested in chaos can get behind this as well,” she said.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. The worldwide outbreak has sickened more than 175,000 people and left more than 6,700 people dead. In the United States, there have been more than 4,000 cases and scores of deaths.

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Associated Press writers Michael Balsamo in Washington, David Klepper in Providence, R.I. and Beatrice Dupuy in New York contributed to this report. ___The Associated Press receives support for health and science coverage from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.